Anybody used Geo-thermal AC system in Central Texas, and if so do you
know of any contractors who do it in the area?
We are looking into it, but the basic idea that the ground temp is
65deg @ 5ft below grade seems hard to beleive in this region, where 100
der all summer is common. Anyone have any actual use experience with
Not in TX, but SW KS so the answer to (1) and (2) are--I'm sure there
is somebody and no, I don't know a contractor near you... :)
But, your supposition that 65F at 5-ft all summer is overly optimisitic
is certainly true. However, even if it is as high as 70F, that's a
fair cry better than 100+F for an air-air exchanger. To work well,
you'll definitely want to be 6-ft or deeper and a well-system would be
even better if feasible.
I have actually had a ground-loop system while in E TN, and can attest
it cut our utility bills by well over a third as compared to an old,
tired, air-air system it replaced. I can strongly recommend
WaterFurnace as a manufacturer based on that system and at least at
that time they were pretty selective in dealerships. Even there,
however, the trench was 6-ft, not 5-ft deep although there they laid a
second loop in the same trench about 2-ft above the bottom one. In TX,
that may not be a good option.
The Water Furnace people do a thorough job of analyzing the site
conditions and do detailed sizing calculations. I've not looked
recently, but when I was doing the research before the we did the
system in TN, OSU-Stillwater was _the_ research center for geothermal
and had a web site full of useful information. I would assume you can
also get a good amount from UT as well.
Last thing I'll note--it won't be an inexpensive installation for an
existing house owing to the need for the excavation, etc. That can be
allayed somewhat if it is new construction by judicious scheduling, but
is unavoidable for retrofit. In TN, at the time we did not have access
to gas, so the economics were somewhat tilted. I'm near the point of
needing a replacement system here and am certainly going to investigate
it here even though we have the similar summer climate as you and
colder (or at least longer) winters and do have gas.
Bear in mind the subsurface soil temperature will gradually increase as
global warming continues. That includes limestone strata typical in the
foothills of the TX hill country. As the area becomes drier, due to lack of
rainfall, suspect this will accelerate.
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